About 3'' is the smallest I've ever been. That was after standing outside for a while at a freezing cold soccer game a couple of years ago. I went to piss at halftime and could hardly find my dick once I got to the stall. It was a bit of a scare, but I had a jerk-off later on that night to make myself feel better.

and it doesn't take cold water to do it. A cold swim in the sea, and my dick disappears somewhere up inside behind my belly button, as far as I can tell. Have to send the dogs it to hunt it out again, my bollix hide behind my ears....LOL